Ceramide, which is a sphingolipid, is a lipid contained only in a small amount in whole living body. It has recently been reported that phenomena, such as proliferation, differentiation, and growth inhibition are induced by enhancing production of intracellular ceramide, and thus ceramide is an attractive intracellular signaling molecule capable of controlling proliferation, differentiation, apoptosis, and the like, of cells. Accordingly, it is thought that a ceramide production-accelerating substance is expected to have effects such as suppression of proliferation, induction of differentiation, and induction of apoptosis of animal cells, and consequently is expected to have therapeutic effects on diseases caused by abnormality of proliferation or differentiation of cells, such as inflammatory diseases and malignant tumors (Non-Patent Document 1).
In addition, ceramide, which is a sphingolipid, makes up at least half of lipids contained in horny layer, which is outermost layer of skin, and plays an important role in moisturizing function and barrier function of skin. Ceramide is produced in and secreted from keratinocytes and then functions as forming a lamella structure in intracellular space of the horny layer.
However, there are many reports showing that normal metabolism of ceramide is prevented and thus the amount of ceramide in horny layer is decreased to cause impairment of moisturizing function, barrier function, and the like, of the skin in dermal diseases such as dry skin, xerosis, atopic dermatitis, senile xerosis and psoriasis.
Therefore, a method of supplying the decreased ceramides topically to treat such diseases has been attempted. However, problems included in this method are, for example, difficulty of long-term effect and low stability, and the like.
Meanwhile, it is reported that ceramide shows bone resorption inhibitory action, bone reinforcing action, and alveolar bone loss inhibitory action, is useful for prevention and amelioration of bone and joint diseases, such as osteoporosis, bone fracture, lumbago, and rheumatism (Patent Document 1), and further that it is effective for prevention of periodontal disease (Patent Document 2). Accordingly, a ceramide production-accelerating substance is also expected to show therapeutic effect on such diseases.
Moreover, ceramide is reported to show action of giving body and elasticity to hair and improving feeling thereof (Patent Document 3), and thus a ceramide production-accelerating substance is also expected to show such effects.
Angelicae Dahuricae Radix, Rehmanniae Radix, Atractylodis Rhizoma, Glycyrrhizae Radix, Rhei Rhizoma, Bletilla Tuber, Polygoni Multiflori Radix, Platycodi Radix, Leonuri Herba, and Dioscoreae Rhizoma are all medicinal plants which have been used since a long time ago as a folk medicine or herbal medicine. Specifically, Angelicae Dahuricae Radix is used for the purpose of alleviation of fever, pain relief, detoxication, pus discharge, and the like as a harval medicine, and its ether extract is reported to show blood pressure elevation action and respiratory movement excitation action (Non-Patent Document 2). Rehmanniae Radix is applied, as a tonic medicine or antipyretic drug, to diabetes, prostatomegaly, senile lumbago, cataract, and the like, and is used as a Chinese medicine for the purpose of blood replenishment, tonic, alleviation of fever, antidiarrheal, laxativeness, and the like. Also, a water extract or ethanol extract of Rehmanniae Radix is reported to show hypoglycemic or hyperglycemic inhibitory action, laxativeness, and diuretic action (Non-Patent Document 3). Atractylodis Rhizoma is used for the purpose of stomach strengthening, intestinal function regulation, diuresis, suppression of sweating, and the like, and is reported to show urinary volume increasing action and hyperglycemic action. Glycyrrhizae Radix is known as a source for glycyrrhizinic acid and it is widely used as an antitussive or expectorant drug, or a remedy for gastrointestinal ulcer, and is used as a Chinese medicine for the purpose of pain relief, detoxication, and the like. An extract of Glycyrrhizae Radix is reported to show remarkable gastric inhibitory action, gastrointestinal ulcer recovery accelerating action, antispasmodic action, antitussive action, and the like (Non-Patent Document 4). Rhei Rhizoma is used as a purgative and a stomachic, and is used as a Chinese medicine for the purpose of anti-inflammation, purgation, and detoxication. Bletilla Tuber is used as a Chinese medicine for the purpose of hemostasis, pain relief, and chronic gastritis (Non-Patent Document 5). Polygoni Multiflori Radix is used as a Chinese medicine for dizziness or headache due to anemia, and insomnia. Platycodi Radix is used as an antitussive and expectorant drug, and is known to have saliva secretion and respiratory secretion accelerating action. Leonuri Herba is used against various symptoms of women before and after childbirth as a medicine for blood activation, increased metabolism, and energy supplement, and is reported to be effective against edema due to nephritis (Non-Patent Document 6). Dioscoreae Rhizoma is used for the purpose of nutritional fortification, antitussive, antidiarrheal, and dryness relief, and is reported to show antihypertensive action and androgenic hormone enhancing action (Non-Patent Document 7).
However, it has not so far been known that these plants show a ceramide production-accelerating effect and a moisturizing effect.    [Patent Document 1] JP-A-2001-158736    [Patent Document 2] JP-A-2001-158735    [Patent Document 3] JP-A-H10-152421    [Non-Patent Document 1] Sphingolipid targets in cancer therapy, David E. Modrak et al., Molecular Cancer Therapeutics, 2006, 5(2): 200-8    [Non-Patent Document 2] Tennen iyaku shigengaku (Natural Medicinal Resources) (2nd Edition, edited by Tadahiro TAKEDA et al., and published by Hirokawa-shoten), pp. 215-216    [Non-Patent Document 3] Tennen iyaku shigengaku (Natural Medicinal Resources) (2nd Edition, edited by Tadahiro TAKEDA et al., and published by Hirokawa-shoten), pp. 132-133    [Non-Patent Document 4] Wakan yakubutsugaku (Japanese, Chinese Medicines) (1st Edition, edited by Keijiro TAKAGI et al., and published by Nanzando), pp. 72-73.    [Non-Patent Document 5] Tennen iyaku shigengaku (Natural Medicinal Resources) (2nd Edition, edited by Tadahiro TAKEDA et al., and published by Hirokawa-shoten), pp. 263-264    [Non-Patent Document 6] Wakan Yakuyo shokubutsu (Japanese and Chinese Medicinal Plants) (20th Edition, edited by Tatsuo KARIBE, and published by Hirokawa-shoten), p. 72    [Non-Patent Document 7] Tennen iyaku shigengaku (Natural Medicinal Resources) (2nd Edition, edited by Tadahiro TAKEDA et al., and published by Hirokawa-shoten), pp. 263-264